export function registerGLTFLoader(THREE) {

  /**
 * @author Rich Tibbett / https://github.com/richtr
 * @author mrdoob / http://mrdoob.com/
 * @author Tony Parisi / http://www.tonyparisi.com/
 * @author Takahiro / https://github.com/takahirox
 * @author Don McCurdy / https://www.donmccurdy.com
 */

  THREE.GLTFLoader = (function () {

    function GLTFLoader(manager) {

      this.manager = (manager !== undefined) ? manager : THREE.DefaultLoadingManager;
      this.dracoLoader = null;
      this.ddsLoader = null;

    }

    GLTFLoader.prototype = {

      constructor: GLTFLoader,

      crossOrigin: 'anonymous',

      load: function (url, onLoad, onProgress, onError) {

        var scope = this;

        var resourcePath;

        if (this.resourcePath !== undefined) {

          resourcePath = this.resourcePath;

        } else if (this.path !== undefined) {

          resourcePath = this.path;

        } else {

          resourcePath = THREE.LoaderUtils.extractUrlBase(url);

        }

        // Tells the LoadingManager to track an extra item, which resolves after
        // the model is fully loaded. This means the count of items loaded will
        // be incorrect, but ensures manager.onLoad() does not fire early.
        scope.manager.itemStart(url);

        var _onError = function (e) {

          if (onError) {

            onError(e);

          } else {

            console.error(e);

          }

          scope.manager.itemError(url);
          scope.manager.itemEnd(url);

        };

        var loader = new THREE.FileLoader(scope.manager);

        loader.setPath(this.path);
        loader.setResponseType('arraybuffer');

        if (scope.crossOrigin === 'use-credentials') {

          loader.setWithCredentials(true);

        }

        loader.load(url, function (data) {

          try {

            scope.parse(data, resourcePath, function (gltf) {

              onLoad(gltf);

              scope.manager.itemEnd(url);

            }, _onError);

          } catch (e) {

            _onError(e);

          }

        }, onProgress, _onError);

      },

      setCrossOrigin: function (value) {

        this.crossOrigin = value;
        return this;

      },

      setPath: function (value) {

        this.path = value;
        return this;

      },

      setResourcePath: function (value) {

        this.resourcePath = value;
        return this;

      },

      setDRACOLoader: function (dracoLoader) {

        this.dracoLoader = dracoLoader;
        return this;

      },

      setDDSLoader: function (ddsLoader) {

        this.ddsLoader = ddsLoader;
        return this;

      },

      parse: function (data, path, onLoad, onError) {

        var content;
        var extensions = {};

        if (typeof data === 'string') {

          content = data;

        } else {

          var magic = THREE.LoaderUtils.decodeText(new Uint8Array(data, 0, 4));

          if (magic === BINARY_EXTENSION_HEADER_MAGIC) {

            try {

              extensions[EXTENSIONS.KHR_BINARY_GLTF] = new GLTFBinaryExtension(data);

            } catch (error) {

              if (onError) onError(error);
              return;

            }

            content = extensions[EXTENSIONS.KHR_BINARY_GLTF].content;

          } else {

            content = THREE.LoaderUtils.decodeText(new Uint8Array(data));

          }

        }

        var json = JSON.parse(content);

        if (json.asset === undefined || json.asset.version[0] < 2) {

          if (onError) onError(new Error('THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported. Use LegacyGLTFLoader instead.'));
          return;

        }

        if (json.extensionsUsed) {

          for (var i = 0; i < json.extensionsUsed.length; ++i) {

            var extensionName = json.extensionsUsed[i];
            var extensionsRequired = json.extensionsRequired || [];

            switch (extensionName) {

              case EXTENSIONS.KHR_LIGHTS_PUNCTUAL:
                extensions[extensionName] = new GLTFLightsExtension(json);
                break;

              case EXTENSIONS.KHR_MATERIALS_UNLIT:
                extensions[extensionName] = new GLTFMaterialsUnlitExtension();
                break;

              case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
                extensions[extensionName] = new GLTFMaterialsPbrSpecularGlossinessExtension();
                break;

              case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
                extensions[extensionName] = new GLTFDracoMeshCompressionExtension(json, this.dracoLoader);
                break;

              case EXTENSIONS.MSFT_TEXTURE_DDS:
                extensions[EXTENSIONS.MSFT_TEXTURE_DDS] = new GLTFTextureDDSExtension(this.ddsLoader);
                break;

              case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
                extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] = new GLTFTextureTransformExtension();
                break;

              default:

                if (extensionsRequired.indexOf(extensionName) >= 0) {

                  console.warn('THREE.GLTFLoader: Unknown extension "' + extensionName + '".');

                }

            }

          }

        }

        var parser = new GLTFParser(json, extensions, {

          path: path || this.resourcePath || '',
          crossOrigin: this.crossOrigin,
          manager: this.manager

        });

        parser.parse(onLoad, onError);

      }

    };

    /* GLTFREGISTRY */

    function GLTFRegistry() {

      var objects = {};

      return {

        get: function (key) {

          return objects[key];

        },

        add: function (key, object) {

          objects[key] = object;

        },

        remove: function (key) {

          delete objects[key];

        },

        removeAll: function () {

          objects = {};

        }

      };

    }

    /*********************************/
    /********** EXTENSIONS ***********/
    /*********************************/

    var EXTENSIONS = {
      KHR_BINARY_GLTF: 'KHR_binary_glTF',
      KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
      KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
      KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
      KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
      KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
      MSFT_TEXTURE_DDS: 'MSFT_texture_dds'
    };

    /**
     * DDS Texture Extension
     *
     * Specification:
     * https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_texture_dds
     *
     */
    function GLTFTextureDDSExtension(ddsLoader) {

      if (!ddsLoader) {

        throw new Error('THREE.GLTFLoader: Attempting to load .dds texture without importing THREE.DDSLoader');

      }

      this.name = EXTENSIONS.MSFT_TEXTURE_DDS;
      this.ddsLoader = ddsLoader;

    }

    /**
     * Lights Extension
     *
     * Specification: PENDING
     */
    function GLTFLightsExtension(json) {

      this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;

      var extension = (json.extensions && json.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL]) || {};
      this.lightDefs = extension.lights || [];

    }

    GLTFLightsExtension.prototype.loadLight = function (lightIndex) {

      var lightDef = this.lightDefs[lightIndex];
      var lightNode;

      var color = new THREE.Color(0xffffff);
      if (lightDef.color !== undefined) color.fromArray(lightDef.color);

      var range = lightDef.range !== undefined ? lightDef.range : 0;

      switch (lightDef.type) {

        case 'directional':
          lightNode = new THREE.DirectionalLight(color);
          lightNode.target.position.set(0, 0, - 1);
          lightNode.add(lightNode.target);
          break;

        case 'point':
          lightNode = new THREE.PointLight(color);
          lightNode.distance = range;
          break;

        case 'spot':
          lightNode = new THREE.SpotLight(color);
          lightNode.distance = range;
          // Handle spotlight properties.
          lightDef.spot = lightDef.spot || {};
          lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
          lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
          lightNode.angle = lightDef.spot.outerConeAngle;
          lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
          lightNode.target.position.set(0, 0, - 1);
          lightNode.add(lightNode.target);
          break;

        default:
          throw new Error('THREE.GLTFLoader: Unexpected light type, "' + lightDef.type + '".');

      }

      // Some lights (e.g. spot) default to a position other than the origin. Reset the position
      // here, because node-level parsing will only override position if explicitly specified.
      lightNode.position.set(0, 0, 0);

      lightNode.decay = 2;

      if (lightDef.intensity !== undefined) lightNode.intensity = lightDef.intensity;

      lightNode.name = lightDef.name || ('light_' + lightIndex);

      return Promise.resolve(lightNode);

    };

    /**
     * Unlit Materials Extension (pending)
     *
     * PR: https://github.com/KhronosGroup/glTF/pull/1163
     */
    function GLTFMaterialsUnlitExtension() {

      this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;

    }

    GLTFMaterialsUnlitExtension.prototype.getMaterialType = function () {

      return THREE.MeshBasicMaterial;

    };

    GLTFMaterialsUnlitExtension.prototype.extendParams = function (materialParams, materialDef, parser) {

      var pending = [];

      materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
      materialParams.opacity = 1.0;

      var metallicRoughness = materialDef.pbrMetallicRoughness;

      if (metallicRoughness) {

        if (Array.isArray(metallicRoughness.baseColorFactor)) {

          var array = metallicRoughness.baseColorFactor;

          materialParams.color.fromArray(array);
          materialParams.opacity = array[3];

        }

        if (metallicRoughness.baseColorTexture !== undefined) {

          pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));

        }

      }

      return Promise.all(pending);

    };

    /* BINARY EXTENSION */
    var BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
    var BINARY_EXTENSION_HEADER_LENGTH = 12;
    var BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };

    function GLTFBinaryExtension(data) {

      this.name = EXTENSIONS.KHR_BINARY_GLTF;
      this.content = null;
      this.body = null;

      var headerView = new DataView(data, 0, BINARY_EXTENSION_HEADER_LENGTH);

      this.header = {
        magic: THREE.LoaderUtils.decodeText(new Uint8Array(data.slice(0, 4))),
        version: headerView.getUint32(4, true),
        length: headerView.getUint32(8, true)
      };

      if (this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC) {

        throw new Error('THREE.GLTFLoader: Unsupported glTF-Binary header.');

      } else if (this.header.version < 2.0) {

        throw new Error('THREE.GLTFLoader: Legacy binary file detected. Use LegacyGLTFLoader instead.');

      }

      var chunkView = new DataView(data, BINARY_EXTENSION_HEADER_LENGTH);
      var chunkIndex = 0;

      while (chunkIndex < chunkView.byteLength) {

        var chunkLength = chunkView.getUint32(chunkIndex, true);
        chunkIndex += 4;

        var chunkType = chunkView.getUint32(chunkIndex, true);
        chunkIndex += 4;

        if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON) {

          var contentArray = new Uint8Array(data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength);
          this.content = THREE.LoaderUtils.decodeText(contentArray);

        } else if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN) {

          var byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
          this.body = data.slice(byteOffset, byteOffset + chunkLength);

        }

        // Clients must ignore chunks with unknown types.

        chunkIndex += chunkLength;

      }

      if (this.content === null) {

        throw new Error('THREE.GLTFLoader: JSON content not found.');

      }

    }

    /**
     * DRACO Mesh Compression Extension
     *
     * Specification: https://github.com/KhronosGroup/glTF/pull/874
     */
    function GLTFDracoMeshCompressionExtension(json, dracoLoader) {

      if (!dracoLoader) {

        throw new Error('THREE.GLTFLoader: No DRACOLoader instance provided.');

      }

      this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
      this.json = json;
      this.dracoLoader = dracoLoader;

    }

    GLTFDracoMeshCompressionExtension.prototype.decodePrimitive = function (primitive, parser) {

      var json = this.json;
      var dracoLoader = this.dracoLoader;
      var bufferViewIndex = primitive.extensions[this.name].bufferView;
      var gltfAttributeMap = primitive.extensions[this.name].attributes;
      var threeAttributeMap = {};
      var attributeNormalizedMap = {};
      var attributeTypeMap = {};

      for (var attributeName in gltfAttributeMap) {

        var threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();

        threeAttributeMap[threeAttributeName] = gltfAttributeMap[attributeName];

      }

      for (attributeName in primitive.attributes) {

        var threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase();

        if (gltfAttributeMap[attributeName] !== undefined) {

          var accessorDef = json.accessors[primitive.attributes[attributeName]];
          var componentType = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

          attributeTypeMap[threeAttributeName] = componentType;
          attributeNormalizedMap[threeAttributeName] = accessorDef.normalized === true;

        }

      }

      return parser.getDependency('bufferView', bufferViewIndex).then(function (bufferView) {

        return new Promise(function (resolve) {

          dracoLoader.decodeDracoFile(bufferView, function (geometry) {

            for (var attributeName in geometry.attributes) {

              var attribute = geometry.attributes[attributeName];
              var normalized = attributeNormalizedMap[attributeName];

              if (normalized !== undefined) attribute.normalized = normalized;

            }

            resolve(geometry);

          }, threeAttributeMap, attributeTypeMap);

        });

      });

    };

    /**
     * Texture Transform Extension
     *
     * Specification:
     */
    function GLTFTextureTransformExtension() {

      this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;

    }

    GLTFTextureTransformExtension.prototype.extendTexture = function (texture, transform) {

      texture = texture.clone();

      if (transform.offset !== undefined) {

        texture.offset.fromArray(transform.offset);

      }

      if (transform.rotation !== undefined) {

        texture.rotation = transform.rotation;

      }

      if (transform.scale !== undefined) {

        texture.repeat.fromArray(transform.scale);

      }

      if (transform.texCoord !== undefined) {

        console.warn('THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.');

      }

      texture.needsUpdate = true;

      return texture;

    };

    /**
     * Specular-Glossiness Extension
     *
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
     */
    function GLTFMaterialsPbrSpecularGlossinessExtension() {

      return {

        name: EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS,

        specularGlossinessParams: [
          'color',
          'map',
          'lightMap',
          'lightMapIntensity',
          'aoMap',
          'aoMapIntensity',
          'emissive',
          'emissiveIntensity',
          'emissiveMap',
          'bumpMap',
          'bumpScale',
          'normalMap',
          'displacementMap',
          'displacementScale',
          'displacementBias',
          'specularMap',
          'specular',
          'glossinessMap',
          'glossiness',
          'alphaMap',
          'envMap',
          'envMapIntensity',
          'refractionRatio',
        ],

        getMaterialType: function () {

          return THREE.ShaderMaterial;

        },

        extendParams: function (materialParams, materialDef, parser) {

          var pbrSpecularGlossiness = materialDef.extensions[this.name];

          var shader = THREE.ShaderLib['standard'];

          var uniforms = THREE.UniformsUtils.clone(shader.uniforms);

          var specularMapParsFragmentChunk = [
            '#ifdef USE_SPECULARMAP',
            '	uniform sampler2D specularMap;',
            '#endif'
          ].join('\n');

          var glossinessMapParsFragmentChunk = [
            '#ifdef USE_GLOSSINESSMAP',
            '	uniform sampler2D glossinessMap;',
            '#endif'
          ].join('\n');

          var specularMapFragmentChunk = [
            'vec3 specularFactor = specular;',
            '#ifdef USE_SPECULARMAP',
            '	vec4 texelSpecular = texture2D( specularMap, vUv );',
            '	texelSpecular = sRGBToLinear( texelSpecular );',
            '	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
            '	specularFactor *= texelSpecular.rgb;',
            '#endif'
          ].join('\n');

          var glossinessMapFragmentChunk = [
            'float glossinessFactor = glossiness;',
            '#ifdef USE_GLOSSINESSMAP',
            '	vec4 texelGlossiness = texture2D( glossinessMap, vUv );',
            '	// reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture',
            '	glossinessFactor *= texelGlossiness.a;',
            '#endif'
          ].join('\n');

          var lightPhysicalFragmentChunk = [
            'PhysicalMaterial material;',
            'material.diffuseColor = diffuseColor.rgb;',
            'material.specularRoughness = clamp( 1.0 - glossinessFactor, 0.04, 1.0 );',
            'material.specularColor = specularFactor.rgb;',
          ].join('\n');

          var fragmentShader = shader.fragmentShader
            .replace('uniform float roughness;', 'uniform vec3 specular;')
            .replace('uniform float metalness;', 'uniform float glossiness;')
            .replace('#include <roughnessmap_pars_fragment>', specularMapParsFragmentChunk)
            .replace('#include <metalnessmap_pars_fragment>', glossinessMapParsFragmentChunk)
            .replace('#include <roughnessmap_fragment>', specularMapFragmentChunk)
            .replace('#include <metalnessmap_fragment>', glossinessMapFragmentChunk)
            .replace('#include <lights_physical_fragment>', lightPhysicalFragmentChunk);

          delete uniforms.roughness;
          delete uniforms.metalness;
          delete uniforms.roughnessMap;
          delete uniforms.metalnessMap;

          uniforms.specular = { value: new THREE.Color().setHex(0x111111) };
          uniforms.glossiness = { value: 0.5 };
          uniforms.specularMap = { value: null };
          uniforms.glossinessMap = { value: null };

          materialParams.vertexShader = shader.vertexShader;
          materialParams.fragmentShader = fragmentShader;
          materialParams.uniforms = uniforms;
          materialParams.defines = { 'STANDARD': '' }

          materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
          materialParams.opacity = 1.0;

          var pending = [];

          if (Array.isArray(pbrSpecularGlossiness.diffuseFactor)) {

            var array = pbrSpecularGlossiness.diffuseFactor;

            materialParams.color.fromArray(array);
            materialParams.opacity = array[3];

          }

          if (pbrSpecularGlossiness.diffuseTexture !== undefined) {

            pending.push(parser.assignTexture(materialParams, 'map', pbrSpecularGlossiness.diffuseTexture));

          }

          materialParams.emissive = new THREE.Color(0.0, 0.0, 0.0);
          materialParams.glossiness = pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0;
          materialParams.specular = new THREE.Color(1.0, 1.0, 1.0);

          if (Array.isArray(pbrSpecularGlossiness.specularFactor)) {

            materialParams.specular.fromArray(pbrSpecularGlossiness.specularFactor);

          }

          if (pbrSpecularGlossiness.specularGlossinessTexture !== undefined) {

            var specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
            pending.push(parser.assignTexture(materialParams, 'glossinessMap', specGlossMapDef));
            pending.push(parser.assignTexture(materialParams, 'specularMap', specGlossMapDef));

          }

          return Promise.all(pending);

        },

        createMaterial: function (params) {

          // setup material properties based on MeshStandardMaterial for Specular-Glossiness

          var material = new THREE.ShaderMaterial({
            defines: params.defines,
            vertexShader: params.vertexShader,
            fragmentShader: params.fragmentShader,
            uniforms: params.uniforms,
            fog: true,
            lights: true,
            opacity: params.opacity,
            transparent: params.transparent
          });

          material.isGLTFSpecularGlossinessMaterial = true;

          material.color = params.color;

          material.map = params.map === undefined ? null : params.map;

          material.lightMap = null;
          material.lightMapIntensity = 1.0;

          material.aoMap = params.aoMap === undefined ? null : params.aoMap;
          material.aoMapIntensity = 1.0;

          material.emissive = params.emissive;
          material.emissiveIntensity = 1.0;
          material.emissiveMap = params.emissiveMap === undefined ? null : params.emissiveMap;

          material.bumpMap = params.bumpMap === undefined ? null : params.bumpMap;
          material.bumpScale = 1;

          material.normalMap = params.normalMap === undefined ? null : params.normalMap;

          if (params.normalScale) material.normalScale = params.normalScale;

          material.displacementMap = null;
          material.displacementScale = 1;
          material.displacementBias = 0;

          material.specularMap = params.specularMap === undefined ? null : params.specularMap;
          material.specular = params.specular;

          material.glossinessMap = params.glossinessMap === undefined ? null : params.glossinessMap;
          material.glossiness = params.glossiness;

          material.alphaMap = null;

          material.envMap = params.envMap === undefined ? null : params.envMap;
          material.envMapIntensity = 1.0;

          material.refractionRatio = 0.98;

          material.extensions.derivatives = true;

          return material;

        },

        /**
         * Clones a GLTFSpecularGlossinessMaterial instance. The ShaderMaterial.copy() method can
         * copy only properties it knows about or inherits, and misses many properties that would
         * normally be defined by MeshStandardMaterial.
         *
         * This method allows GLTFSpecularGlossinessMaterials to be cloned in the process of
         * loading a glTF model, but cloning later (e.g. by the user) would require these changes
         * AND also updating `.onBeforeRender` on the parent mesh.
         *
         * @param  {THREE.ShaderMaterial} source
         * @return {THREE.ShaderMaterial}
         */
        cloneMaterial: function (source) {

          var target = source.clone();

          target.isGLTFSpecularGlossinessMaterial = true;

          var params = this.specularGlossinessParams;

          for (var i = 0, il = params.length; i < il; i++) {

            var value = source[params[i]];
            target[params[i]] = (value && value.isColor) ? value.clone() : value;

          }

          return target;

        },

        // Here's based on refreshUniformsCommon() and refreshUniformsStandard() in WebGLRenderer.
        refreshUniforms: function (renderer, scene, camera, geometry, material) {

          if (material.isGLTFSpecularGlossinessMaterial !== true) {

            return;

          }

          var uniforms = material.uniforms;
          var defines = material.defines;

          uniforms.opacity.value = material.opacity;

          uniforms.diffuse.value.copy(material.color);
          uniforms.emissive.value.copy(material.emissive).multiplyScalar(material.emissiveIntensity);

          uniforms.map.value = material.map;
          uniforms.specularMap.value = material.specularMap;
          uniforms.alphaMap.value = material.alphaMap;

          uniforms.lightMap.value = material.lightMap;
          uniforms.lightMapIntensity.value = material.lightMapIntensity;

          uniforms.aoMap.value = material.aoMap;
          uniforms.aoMapIntensity.value = material.aoMapIntensity;

          // uv repeat and offset setting priorities
          // 1. color map
          // 2. specular map
          // 3. normal map
          // 4. bump map
          // 5. alpha map
          // 6. emissive map

          var uvScaleMap;

          if (material.map) {

            uvScaleMap = material.map;

          } else if (material.specularMap) {

            uvScaleMap = material.specularMap;

          } else if (material.displacementMap) {

            uvScaleMap = material.displacementMap;

          } else if (material.normalMap) {

            uvScaleMap = material.normalMap;

          } else if (material.bumpMap) {

            uvScaleMap = material.bumpMap;

          } else if (material.glossinessMap) {

            uvScaleMap = material.glossinessMap;

          } else if (material.alphaMap) {

            uvScaleMap = material.alphaMap;

          } else if (material.emissiveMap) {

            uvScaleMap = material.emissiveMap;

          }

          if (uvScaleMap !== undefined) {

            // backwards compatibility
            if (uvScaleMap.isWebGLRenderTarget) {

              uvScaleMap = uvScaleMap.texture;

            }

            if (uvScaleMap.matrixAutoUpdate === true) {

              uvScaleMap.updateMatrix();

            }

            uniforms.uvTransform.value.copy(uvScaleMap.matrix);

          }

          if (material.envMap) {

            uniforms.envMap.value = material.envMap;
            uniforms.envMapIntensity.value = material.envMapIntensity;

            // don't flip CubeTexture envMaps, flip everything else:
            //  WebGLRenderTargetCube will be flipped for backwards compatibility
            //  WebGLRenderTargetCube.texture will be flipped because it's a Texture and NOT a CubeTexture
            // this check must be handled differently, or removed entirely, if WebGLRenderTargetCube uses a CubeTexture in the future
            uniforms.flipEnvMap.value = material.envMap.isCubeTexture ? - 1 : 1;

            uniforms.reflectivity.value = material.reflectivity;
            uniforms.refractionRatio.value = material.refractionRatio;

            uniforms.maxMipLevel.value = renderer.properties.get(material.envMap).__maxMipLevel;

          }

          uniforms.specular.value.copy(material.specular);
          uniforms.glossiness.value = material.glossiness;

          uniforms.glossinessMap.value = material.glossinessMap;

          uniforms.emissiveMap.value = material.emissiveMap;
          uniforms.bumpMap.value = material.bumpMap;
          uniforms.normalMap.value = material.normalMap;

          uniforms.displacementMap.value = material.displacementMap;
          uniforms.displacementScale.value = material.displacementScale;
          uniforms.displacementBias.value = material.displacementBias;

          if (uniforms.glossinessMap.value !== null && defines.USE_GLOSSINESSMAP === undefined) {

            defines.USE_GLOSSINESSMAP = '';
            // set USE_ROUGHNESSMAP to enable vUv
            defines.USE_ROUGHNESSMAP = '';

          }

          if (uniforms.glossinessMap.value === null && defines.USE_GLOSSINESSMAP !== undefined) {

            delete defines.USE_GLOSSINESSMAP;
            delete defines.USE_ROUGHNESSMAP;

          }

        }

      };

    }

    /*********************************/
    /********** INTERPOLATION ********/
    /*********************************/

    // Spline Interpolation
    // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
    function GLTFCubicSplineInterpolant(parameterPositions, sampleValues, sampleSize, resultBuffer) {

      THREE.Interpolant.call(this, parameterPositions, sampleValues, sampleSize, resultBuffer);

    }

    GLTFCubicSplineInterpolant.prototype = Object.create(THREE.Interpolant.prototype);
    GLTFCubicSplineInterpolant.prototype.constructor = GLTFCubicSplineInterpolant;

    GLTFCubicSplineInterpolant.prototype.copySampleValue_ = function (index) {

      // Copies a sample value to the result buffer. See description of glTF
      // CUBICSPLINE values layout in interpolate_() function below.

      var result = this.resultBuffer,
        values = this.sampleValues,
        valueSize = this.valueSize,
        offset = index * valueSize * 3 + valueSize;

      for (var i = 0; i !== valueSize; i++) {

        result[i] = values[offset + i];

      }

      return result;

    };

    GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

    GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

    GLTFCubicSplineInterpolant.prototype.interpolate_ = function (i1, t0, t, t1) {

      var result = this.resultBuffer;
      var values = this.sampleValues;
      var stride = this.valueSize;

      var stride2 = stride * 2;
      var stride3 = stride * 3;

      var td = t1 - t0;

      var p = (t - t0) / td;
      var pp = p * p;
      var ppp = pp * p;

      var offset1 = i1 * stride3;
      var offset0 = offset1 - stride3;

      var s2 = - 2 * ppp + 3 * pp;
      var s3 = ppp - pp;
      var s0 = 1 - s2;
      var s1 = s3 - pp + p;

      // Layout of keyframe output values for CUBICSPLINE animations:
      //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
      for (var i = 0; i !== stride; i++) {

        var p0 = values[offset0 + i + stride]; // splineVertex_k
        var m0 = values[offset0 + i + stride2] * td; // outTangent_k * (t_k+1 - t_k)
        var p1 = values[offset1 + i + stride]; // splineVertex_k+1
        var m1 = values[offset1 + i] * td; // inTangent_k+1 * (t_k+1 - t_k)

        result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;

      }

      return result;

    };

    /*********************************/
    /********** INTERNALS ************/
    /*********************************/

    /* CONSTANTS */

    var WEBGL_CONSTANTS = {
      FLOAT: 5126,
      //FLOAT_MAT2: 35674,
      FLOAT_MAT3: 35675,
      FLOAT_MAT4: 35676,
      FLOAT_VEC2: 35664,
      FLOAT_VEC3: 35665,
      FLOAT_VEC4: 35666,
      LINEAR: 9729,
      REPEAT: 10497,
      SAMPLER_2D: 35678,
      POINTS: 0,
      LINES: 1,
      LINE_LOOP: 2,
      LINE_STRIP: 3,
      TRIANGLES: 4,
      TRIANGLE_STRIP: 5,
      TRIANGLE_FAN: 6,
      UNSIGNED_BYTE: 5121,
      UNSIGNED_SHORT: 5123
    };

    var WEBGL_COMPONENT_TYPES = {
      5120: Int8Array,
      5121: Uint8Array,
      5122: Int16Array,
      5123: Uint16Array,
      5125: Uint32Array,
      5126: Float32Array
    };

    var WEBGL_FILTERS = {
      9728: THREE.NearestFilter,
      9729: THREE.LinearFilter,
      9984: THREE.NearestMipmapNearestFilter,
      9985: THREE.LinearMipmapNearestFilter,
      9986: THREE.NearestMipmapLinearFilter,
      9987: THREE.LinearMipmapLinearFilter
    };

    var WEBGL_WRAPPINGS = {
      33071: THREE.ClampToEdgeWrapping,
      33648: THREE.MirroredRepeatWrapping,
      10497: THREE.RepeatWrapping
    };

    var WEBGL_TYPE_SIZES = {
      'SCALAR': 1,
      'VEC2': 2,
      'VEC3': 3,
      'VEC4': 4,
      'MAT2': 4,
      'MAT3': 9,
      'MAT4': 16
    };

    var ATTRIBUTES = {
      POSITION: 'position',
      NORMAL: 'normal',
      TANGENT: 'tangent',
      TEXCOORD_0: 'uv',
      TEXCOORD_1: 'uv2',
      COLOR_0: 'color',
      WEIGHTS_0: 'skinWeight',
      JOINTS_0: 'skinIndex',
    };

    var PATH_PROPERTIES = {
      scale: 'scale',
      translation: 'position',
      rotation: 'quaternion',
      weights: 'morphTargetInfluences'
    };

    var INTERPOLATION = {
      CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
      // keyframe track will be initialized with a default interpolation type, then modified.
      LINEAR: THREE.InterpolateLinear,
      STEP: THREE.InterpolateDiscrete
    };

    var ALPHA_MODES = {
      OPAQUE: 'OPAQUE',
      MASK: 'MASK',
      BLEND: 'BLEND'
    };

    var MIME_TYPE_FORMATS = {
      'image/png': THREE.RGBAFormat,
      'image/jpeg': THREE.RGBFormat
    };

    /* UTILITY FUNCTIONS */

    function resolveURL(url, path) {

      // Invalid URL
      if (typeof url !== 'string' || url === '') return '';

      // Host Relative URL
      if (/^https?:\/\//i.test(path) && /^\//.test(url)) {

        path = path.replace(/(^https?:\/\/[^\/]+).*/i, '$1');

      }

      // Absolute URL http://,https://,//
      if (/^(https?:)?\/\//i.test(url)) return url;

      // Data URI
      if (/^data:.*,.*$/i.test(url)) return url;

      // Blob URL
      if (/^blob:.*$/i.test(url)) return url;

      // Relative URL
      return path + url;

    }

    var defaultMaterial;

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
     */
    function createDefaultMaterial() {

      defaultMaterial = defaultMaterial || new THREE.MeshStandardMaterial({
        color: 0xFFFFFF,
        emissive: 0x000000,
        metalness: 1,
        roughness: 1,
        transparent: false,
        depthTest: true,
        side: THREE.FrontSide
      });

      return defaultMaterial;

    }

    function addUnknownExtensionsToUserData(knownExtensions, object, objectDef) {

      // Add unknown glTF extensions to an object's userData.

      for (var name in objectDef.extensions) {

        if (knownExtensions[name] === undefined) {

          object.userData.gltfExtensions = object.userData.gltfExtensions || {};
          object.userData.gltfExtensions[name] = objectDef.extensions[name];

        }

      }

    }

    /**
     * @param {THREE.Object3D|THREE.Material|THREE.BufferGeometry} object
     * @param {GLTF.definition} gltfDef
     */
    function assignExtrasToUserData(object, gltfDef) {

      if (gltfDef.extras !== undefined) {

        if (typeof gltfDef.extras === 'object') {

          Object.assign(object.userData, gltfDef.extras);

        } else {

          console.warn('THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras);

        }

      }

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
     *
     * @param {THREE.BufferGeometry} geometry
     * @param {Array<GLTF.Target>} targets
     * @param {GLTFParser} parser
     * @return {Promise<THREE.BufferGeometry>}
     */
    function addMorphTargets(geometry, targets, parser) {

      var hasMorphPosition = false;
      var hasMorphNormal = false;

      for (var i = 0, il = targets.length; i < il; i++) {

        var target = targets[i];

        if (target.POSITION !== undefined) hasMorphPosition = true;
        if (target.NORMAL !== undefined) hasMorphNormal = true;

        if (hasMorphPosition && hasMorphNormal) break;

      }

      if (!hasMorphPosition && !hasMorphNormal) return Promise.resolve(geometry);

      var pendingPositionAccessors = [];
      var pendingNormalAccessors = [];

      for (var i = 0, il = targets.length; i < il; i++) {

        var target = targets[i];

        if (hasMorphPosition) {

          var pendingAccessor = target.POSITION !== undefined
            ? parser.getDependency('accessor', target.POSITION)
            : geometry.attributes.position;

          pendingPositionAccessors.push(pendingAccessor);

        }

        if (hasMorphNormal) {

          var pendingAccessor = target.NORMAL !== undefined
            ? parser.getDependency('accessor', target.NORMAL)
            : geometry.attributes.normal;

          pendingNormalAccessors.push(pendingAccessor);

        }

      }

      return Promise.all([
        Promise.all(pendingPositionAccessors),
        Promise.all(pendingNormalAccessors)
      ]).then(function (accessors) {

        var morphPositions = accessors[0];
        var morphNormals = accessors[1];

        // Clone morph target accessors before modifying them.

        for (var i = 0, il = morphPositions.length; i < il; i++) {

          if (geometry.attributes.position === morphPositions[i]) continue;

          morphPositions[i] = cloneBufferAttribute(morphPositions[i]);

        }

        for (var i = 0, il = morphNormals.length; i < il; i++) {

          if (geometry.attributes.normal === morphNormals[i]) continue;

          morphNormals[i] = cloneBufferAttribute(morphNormals[i]);

        }

        for (var i = 0, il = targets.length; i < il; i++) {

          var target = targets[i];
          var attributeName = 'morphTarget' + i;

          if (hasMorphPosition) {

            // Three.js morph position is absolute value. The formula is
            //   basePosition
            //     + weight0 * ( morphPosition0 - basePosition )
            //     + weight1 * ( morphPosition1 - basePosition )
            //     ...
            // while the glTF one is relative
            //   basePosition
            //     + weight0 * glTFmorphPosition0
            //     + weight1 * glTFmorphPosition1
            //     ...
            // then we need to convert from relative to absolute here.

            if (target.POSITION !== undefined) {

              var positionAttribute = morphPositions[i];
              positionAttribute.name = attributeName;

              var position = geometry.attributes.position;

              for (var j = 0, jl = positionAttribute.count; j < jl; j++) {

                positionAttribute.setXYZ(
                  j,
                  positionAttribute.getX(j) + position.getX(j),
                  positionAttribute.getY(j) + position.getY(j),
                  positionAttribute.getZ(j) + position.getZ(j)
                );

              }

            }

          }

          if (hasMorphNormal) {

            // see target.POSITION's comment

            if (target.NORMAL !== undefined) {

              var normalAttribute = morphNormals[i];
              normalAttribute.name = attributeName;

              var normal = geometry.attributes.normal;

              for (var j = 0, jl = normalAttribute.count; j < jl; j++) {

                normalAttribute.setXYZ(
                  j,
                  normalAttribute.getX(j) + normal.getX(j),
                  normalAttribute.getY(j) + normal.getY(j),
                  normalAttribute.getZ(j) + normal.getZ(j)
                );

              }

            }

          }

        }

        if (hasMorphPosition) geometry.morphAttributes.position = morphPositions;
        if (hasMorphNormal) geometry.morphAttributes.normal = morphNormals;

        return geometry;

      });

    }

    /**
     * @param {THREE.Mesh} mesh
     * @param {GLTF.Mesh} meshDef
     */
    function updateMorphTargets(mesh, meshDef) {

      mesh.updateMorphTargets();

      if (meshDef.weights !== undefined) {

        for (var i = 0, il = meshDef.weights.length; i < il; i++) {

          mesh.morphTargetInfluences[i] = meshDef.weights[i];

        }

      }

      // .extras has user-defined data, so check that .extras.targetNames is an array.
      if (meshDef.extras && Array.isArray(meshDef.extras.targetNames)) {

        var targetNames = meshDef.extras.targetNames;

        if (mesh.morphTargetInfluences.length === targetNames.length) {

          mesh.morphTargetDictionary = {};

          for (var i = 0, il = targetNames.length; i < il; i++) {

            mesh.morphTargetDictionary[targetNames[i]] = i;

          }

        } else {

          console.warn('THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.');

        }

      }

    }

    function createPrimitiveKey(primitiveDef) {

      var dracoExtension = primitiveDef.extensions && primitiveDef.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION];
      var geometryKey;

      if (dracoExtension) {

        geometryKey = 'draco:' + dracoExtension.bufferView
          + ':' + dracoExtension.indices
          + ':' + createAttributesKey(dracoExtension.attributes);

      } else {

        geometryKey = primitiveDef.indices + ':' + createAttributesKey(primitiveDef.attributes) + ':' + primitiveDef.mode;

      }

      return geometryKey;

    }

    function createAttributesKey(attributes) {

      var attributesKey = '';

      var keys = Object.keys(attributes).sort();

      for (var i = 0, il = keys.length; i < il; i++) {

        attributesKey += keys[i] + ':' + attributes[keys[i]] + ';';

      }

      return attributesKey;

    }

    function cloneBufferAttribute(attribute) {

      if (attribute.isInterleavedBufferAttribute) {

        var count = attribute.count;
        var itemSize = attribute.itemSize;
        var array = attribute.array.slice(0, count * itemSize);

        for (var i = 0, j = 0; i < count; ++i) {

          array[j++] = attribute.getX(i);
          if (itemSize >= 2) array[j++] = attribute.getY(i);
          if (itemSize >= 3) array[j++] = attribute.getZ(i);
          if (itemSize >= 4) array[j++] = attribute.getW(i);

        }

        return new THREE.BufferAttribute(array, itemSize, attribute.normalized);

      }

      return attribute.clone();

    }

    /* GLTF PARSER */

    function GLTFParser(json, extensions, options) {

      this.json = json || {};
      this.extensions = extensions || {};
      this.options = options || {};

      // loader object cache
      this.cache = new GLTFRegistry();

      // BufferGeometry caching
      this.primitiveCache = {};

      this.textureLoader = new THREE.TextureLoader(this.options.manager);
      this.textureLoader.setCrossOrigin(this.options.crossOrigin);

      this.fileLoader = new THREE.FileLoader(this.options.manager);
      this.fileLoader.setResponseType('arraybuffer');

      if (this.options.crossOrigin === 'use-credentials') {

        this.fileLoader.setWithCredentials(true);

      }

    }

    GLTFParser.prototype.parse = function (onLoad, onError) {

      var parser = this;
      var json = this.json;
      var extensions = this.extensions;

      // Clear the loader cache
      this.cache.removeAll();

      // Mark the special nodes/meshes in json for efficient parse
      this.markDefs();

      Promise.all([

        this.getDependencies('scene'),
        this.getDependencies('animation'),
        this.getDependencies('camera'),

      ]).then(function (dependencies) {

        var result = {
          scene: dependencies[0][json.scene || 0],
          scenes: dependencies[0],
          animations: dependencies[1],
          cameras: dependencies[2],
          asset: json.asset,
          parser: parser,
          userData: {}
        };

        addUnknownExtensionsToUserData(extensions, result, json);

        assignExtrasToUserData(result, json);

        onLoad(result);

      }).catch(onError);

    };

    /**
     * Marks the special nodes/meshes in json for efficient parse.
     */
    GLTFParser.prototype.markDefs = function () {

      var nodeDefs = this.json.nodes || [];
      var skinDefs = this.json.skins || [];
      var meshDefs = this.json.meshes || [];

      var meshReferences = {};
      var meshUses = {};

      // Nothing in the node definition indicates whether it is a Bone or an
      // Object3D. Use the skins' joint references to mark bones.
      for (var skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex++) {

        var joints = skinDefs[skinIndex].joints;

        for (var i = 0, il = joints.length; i < il; i++) {

          nodeDefs[joints[i]].isBone = true;

        }

      }

      // Meshes can (and should) be reused by multiple nodes in a glTF asset. To
      // avoid having more than one THREE.Mesh with the same name, count
      // references and rename instances below.
      //
      // Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
      for (var nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {

        var nodeDef = nodeDefs[nodeIndex];

        if (nodeDef.mesh !== undefined) {

          if (meshReferences[nodeDef.mesh] === undefined) {

            meshReferences[nodeDef.mesh] = meshUses[nodeDef.mesh] = 0;

          }

          meshReferences[nodeDef.mesh]++;

          // Nothing in the mesh definition indicates whether it is
          // a SkinnedMesh or Mesh. Use the node's mesh reference
          // to mark SkinnedMesh if node has skin.
          if (nodeDef.skin !== undefined) {

            meshDefs[nodeDef.mesh].isSkinnedMesh = true;

          }

        }

      }

      this.json.meshReferences = meshReferences;
      this.json.meshUses = meshUses;

    };

    /**
     * Requests the specified dependency asynchronously, with caching.
     * @param {string} type
     * @param {number} index
     * @return {Promise<THREE.Object3D|THREE.Material|THREE.Texture|THREE.AnimationClip|ArrayBuffer|Object>}
     */
    GLTFParser.prototype.getDependency = function (type, index) {

      var cacheKey = type + ':' + index;
      var dependency = this.cache.get(cacheKey);

      if (!dependency) {

        switch (type) {

          case 'scene':
            dependency = this.loadScene(index);
            break;

          case 'node':
            dependency = this.loadNode(index);
            break;

          case 'mesh':
            dependency = this.loadMesh(index);
            break;

          case 'accessor':
            dependency = this.loadAccessor(index);
            break;

          case 'bufferView':
            dependency = this.loadBufferView(index);
            break;

          case 'buffer':
            dependency = this.loadBuffer(index);
            break;

          case 'material':
            dependency = this.loadMaterial(index);
            break;

          case 'texture':
            dependency = this.loadTexture(index);
            break;

          case 'skin':
            dependency = this.loadSkin(index);
            break;

          case 'animation':
            dependency = this.loadAnimation(index);
            break;

          case 'camera':
            dependency = this.loadCamera(index);
            break;

          case 'light':
            dependency = this.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].loadLight(index);
            break;

          default:
            throw new Error('Unknown type: ' + type);

        }

        this.cache.add(cacheKey, dependency);

      }

      return dependency;

    };

    /**
     * Requests all dependencies of the specified type asynchronously, with caching.
     * @param {string} type
     * @return {Promise<Array<Object>>}
     */
    GLTFParser.prototype.getDependencies = function (type) {

      var dependencies = this.cache.get(type);

      if (!dependencies) {

        var parser = this;
        var defs = this.json[type + (type === 'mesh' ? 'es' : 's')] || [];

        dependencies = Promise.all(defs.map(function (def, index) {

          return parser.getDependency(type, index);

        }));

        this.cache.add(type, dependencies);

      }

      return dependencies;

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferIndex
     * @return {Promise<ArrayBuffer>}
     */
    GLTFParser.prototype.loadBuffer = function (bufferIndex) {

      var bufferDef = this.json.buffers[bufferIndex];
      var loader = this.fileLoader;

      if (bufferDef.type && bufferDef.type !== 'arraybuffer') {

        throw new Error('THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.');

      }

      // If present, GLB container is required to be the first buffer.
      if (bufferDef.uri === undefined && bufferIndex === 0) {

        return Promise.resolve(this.extensions[EXTENSIONS.KHR_BINARY_GLTF].body);

      }

      var options = this.options;

      return new Promise(function (resolve, reject) {

        loader.load(resolveURL(bufferDef.uri, options.path), resolve, undefined, function () {

          reject(new Error('THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".'));

        });

      });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
     * @param {number} bufferViewIndex
     * @return {Promise<ArrayBuffer>}
     */
    GLTFParser.prototype.loadBufferView = function (bufferViewIndex) {

      var bufferViewDef = this.json.bufferViews[bufferViewIndex];

      return this.getDependency('buffer', bufferViewDef.buffer).then(function (buffer) {

        var byteLength = bufferViewDef.byteLength || 0;
        var byteOffset = bufferViewDef.byteOffset || 0;
        return buffer.slice(byteOffset, byteOffset + byteLength);

      });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
     * @param {number} accessorIndex
     * @return {Promise<THREE.BufferAttribute|THREE.InterleavedBufferAttribute>}
     */
    GLTFParser.prototype.loadAccessor = function (accessorIndex) {

      var parser = this;
      var json = this.json;

      var accessorDef = this.json.accessors[accessorIndex];

      if (accessorDef.bufferView === undefined && accessorDef.sparse === undefined) {

        // Ignore empty accessors, which may be used to declare runtime
        // information about attributes coming from another source (e.g. Draco
        // compression extension).
        return Promise.resolve(null);

      }

      var pendingBufferViews = [];

      if (accessorDef.bufferView !== undefined) {

        pendingBufferViews.push(this.getDependency('bufferView', accessorDef.bufferView));

      } else {

        pendingBufferViews.push(null);

      }

      if (accessorDef.sparse !== undefined) {

        pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.indices.bufferView));
        pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.values.bufferView));

      }

      return Promise.all(pendingBufferViews).then(function (bufferViews) {

        var bufferView = bufferViews[0];

        var itemSize = WEBGL_TYPE_SIZES[accessorDef.type];
        var TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

        // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
        var elementBytes = TypedArray.BYTES_PER_ELEMENT;
        var itemBytes = elementBytes * itemSize;
        var byteOffset = accessorDef.byteOffset || 0;
        var byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[accessorDef.bufferView].byteStride : undefined;
        var normalized = accessorDef.normalized === true;
        var array, bufferAttribute;

        // The buffer is not interleaved if the stride is the item size in bytes.
        if (byteStride && byteStride !== itemBytes) {

          // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
          // This makes sure that IBA.count reflects accessor.count properly
          var ibSlice = Math.floor(byteOffset / byteStride);
          var ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType + ':' + ibSlice + ':' + accessorDef.count;
          var ib = parser.cache.get(ibCacheKey);

          if (!ib) {

            array = new TypedArray(bufferView, ibSlice * byteStride, accessorDef.count * byteStride / elementBytes);

            // Integer parameters to IB/IBA are in array elements, not bytes.
            ib = new THREE.InterleavedBuffer(array, byteStride / elementBytes);

            parser.cache.add(ibCacheKey, ib);

          }

          bufferAttribute = new THREE.InterleavedBufferAttribute(ib, itemSize, (byteOffset % byteStride) / elementBytes, normalized);

        } else {

          if (bufferView === null) {

            array = new TypedArray(accessorDef.count * itemSize);

          } else {

            array = new TypedArray(bufferView, byteOffset, accessorDef.count * itemSize);

          }

          bufferAttribute = new THREE.BufferAttribute(array, itemSize, normalized);

        }

        // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
        if (accessorDef.sparse !== undefined) {

          var itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
          var TypedArrayIndices = WEBGL_COMPONENT_TYPES[accessorDef.sparse.indices.componentType];

          var byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
          var byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;

          var sparseIndices = new TypedArrayIndices(bufferViews[1], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices);
          var sparseValues = new TypedArray(bufferViews[2], byteOffsetValues, accessorDef.sparse.count * itemSize);

          if (bufferView !== null) {

            // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
            bufferAttribute.setArray(bufferAttribute.array.slice());

          }

          for (var i = 0, il = sparseIndices.length; i < il; i++) {

            var index = sparseIndices[i];

            bufferAttribute.setX(index, sparseValues[i * itemSize]);
            if (itemSize >= 2) bufferAttribute.setY(index, sparseValues[i * itemSize + 1]);
            if (itemSize >= 3) bufferAttribute.setZ(index, sparseValues[i * itemSize + 2]);
            if (itemSize >= 4) bufferAttribute.setW(index, sparseValues[i * itemSize + 3]);
            if (itemSize >= 5) throw new Error('THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.');

          }

        }

        return bufferAttribute;

      });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
     * @param {number} textureIndex
     * @return {Promise<THREE.Texture>}
     */
    GLTFParser.prototype.loadTexture = function (textureIndex) {

      var parser = this;
      var json = this.json;
      var options = this.options;
      var textureLoader = this.textureLoader;

      var URL = window.URL || window.webkitURL;

      var textureDef = json.textures[textureIndex];

      var textureExtensions = textureDef.extensions || {};

      var source;

      if (textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]) {

        source = json.images[textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS].source];

      } else {

        source = json.images[textureDef.source];

      }

      var sourceURI = source.uri;
      var isObjectURL = false;

      if (source.bufferView !== undefined) {

        // Load binary image data from bufferView, if provided.

        sourceURI = parser.getDependency('bufferView', source.bufferView).then(function (bufferView) {

          isObjectURL = true;
          var blob = new Blob([bufferView], { type: source.mimeType });
          sourceURI = URL.createObjectURL(blob);
          return sourceURI;

        });

      }

      return Promise.resolve(sourceURI).then(function (sourceURI) {

        // Load Texture resource.

        var loader = THREE.Loader.Handlers.get(sourceURI);

        if (!loader) {

          loader = textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]
            ? parser.extensions[EXTENSIONS.MSFT_TEXTURE_DDS].ddsLoader
            : textureLoader;

        }

        return new Promise(function (resolve, reject) {

          loader.load(resolveURL(sourceURI, options.path), resolve, undefined, reject);

        });

      }).then(function (texture) {

        // Clean up resources and configure Texture.

        if (isObjectURL === true) {

          URL.revokeObjectURL(sourceURI);

        }

        texture.flipY = false;

        if (textureDef.name !== undefined) texture.name = textureDef.name;

        // Ignore unknown mime types, like DDS files.
        if (source.mimeType in MIME_TYPE_FORMATS) {

          texture.format = MIME_TYPE_FORMATS[source.mimeType];

        }

        var samplers = json.samplers || {};
        var sampler = samplers[textureDef.sampler] || {};

        texture.magFilter = WEBGL_FILTERS[sampler.magFilter] || THREE.LinearFilter;
        texture.minFilter = WEBGL_FILTERS[sampler.minFilter] || THREE.LinearMipmapLinearFilter;
        texture.wrapS = WEBGL_WRAPPINGS[sampler.wrapS] || THREE.RepeatWrapping;
        texture.wrapT = WEBGL_WRAPPINGS[sampler.wrapT] || THREE.RepeatWrapping;

        return texture;

      });

    };

    /**
     * Asynchronously assigns a texture to the given material parameters.
     * @param {Object} materialParams
     * @param {string} mapName
     * @param {Object} mapDef
     * @return {Promise}
     */
    GLTFParser.prototype.assignTexture = function (materialParams, mapName, mapDef) {

      var parser = this;

      return this.getDependency('texture', mapDef.index).then(function (texture) {

        if (!texture.isCompressedTexture) {

          switch (mapName) {

            case 'aoMap':
            case 'emissiveMap':
            case 'metalnessMap':
            case 'normalMap':
            case 'roughnessMap':
              texture.format = THREE.RGBFormat;
              break;

          }

        }

        if (parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]) {

          var transform = mapDef.extensions !== undefined ? mapDef.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] : undefined;

          if (transform) {

            texture = parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM].extendTexture(texture, transform);

          }

        }

        materialParams[mapName] = texture;

      });

    };

    /**
     * Assigns final material to a Mesh, Line, or Points instance. The instance
     * already has a material (generated from the glTF material options alone)
     * but reuse of the same glTF material may require multiple threejs materials
     * to accomodate different primitive types, defines, etc. New materials will
     * be created if necessary, and reused from a cache.
     * @param  {THREE.Object3D} mesh Mesh, Line, or Points instance.
     */
    GLTFParser.prototype.assignFinalMaterial = function (mesh) {

      var geometry = mesh.geometry;
      var material = mesh.material;
      var extensions = this.extensions;

      var useVertexTangents = geometry.attributes.tangent !== undefined;
      var useVertexColors = geometry.attributes.color !== undefined;
      var useFlatShading = geometry.attributes.normal === undefined;
      var useSkinning = mesh.isSkinnedMesh === true;
      var useMorphTargets = Object.keys(geometry.morphAttributes).length > 0;
      var useMorphNormals = useMorphTargets && geometry.morphAttributes.normal !== undefined;

      if (mesh.isPoints) {

        var cacheKey = 'PointsMaterial:' + material.uuid;

        var pointsMaterial = this.cache.get(cacheKey);

        if (!pointsMaterial) {

          pointsMaterial = new THREE.PointsMaterial();
          THREE.Material.prototype.copy.call(pointsMaterial, material);
          pointsMaterial.color.copy(material.color);
          pointsMaterial.map = material.map;
          pointsMaterial.lights = false; // PointsMaterial doesn't support lights yet
          pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px

          this.cache.add(cacheKey, pointsMaterial);

        }

        material = pointsMaterial;

      } else if (mesh.isLine) {

        var cacheKey = 'LineBasicMaterial:' + material.uuid;

        var lineMaterial = this.cache.get(cacheKey);

        if (!lineMaterial) {

          lineMaterial = new THREE.LineBasicMaterial();
          THREE.Material.prototype.copy.call(lineMaterial, material);
          lineMaterial.color.copy(material.color);
          lineMaterial.lights = false; // LineBasicMaterial doesn't support lights yet

          this.cache.add(cacheKey, lineMaterial);

        }

        material = lineMaterial;

      }

      // Clone the material if it will be modified
      if (useVertexTangents || useVertexColors || useFlatShading || useSkinning || useMorphTargets) {

        var cacheKey = 'ClonedMaterial:' + material.uuid + ':';

        if (material.isGLTFSpecularGlossinessMaterial) cacheKey += 'specular-glossiness:';
        if (useSkinning) cacheKey += 'skinning:';
        if (useVertexTangents) cacheKey += 'vertex-tangents:';
        if (useVertexColors) cacheKey += 'vertex-colors:';
        if (useFlatShading) cacheKey += 'flat-shading:';
        if (useMorphTargets) cacheKey += 'morph-targets:';
        if (useMorphNormals) cacheKey += 'morph-normals:';

        var cachedMaterial = this.cache.get(cacheKey);

        if (!cachedMaterial) {

          cachedMaterial = material.isGLTFSpecularGlossinessMaterial
            ? extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].cloneMaterial(material)
            : material.clone();

          if (useSkinning) cachedMaterial.skinning = true;
          if (useVertexTangents) cachedMaterial.vertexTangents = true;
          if (useVertexColors) cachedMaterial.vertexColors = THREE.VertexColors;
          if (useFlatShading) cachedMaterial.flatShading = true;
          if (useMorphTargets) cachedMaterial.morphTargets = true;
          if (useMorphNormals) cachedMaterial.morphNormals = true;

          this.cache.add(cacheKey, cachedMaterial);

        }

        material = cachedMaterial;

      }

      // workarounds for mesh and geometry

      if (material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined) {

        console.log('THREE.GLTFLoader: Duplicating UVs to support aoMap.');
        geometry.addAttribute('uv2', new THREE.BufferAttribute(geometry.attributes.uv.array, 2));

      }

      if (material.isGLTFSpecularGlossinessMaterial) {

        // for GLTFSpecularGlossinessMaterial(ShaderMaterial) uniforms runtime update
        mesh.onBeforeRender = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].refreshUniforms;

      }

      mesh.material = material;

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
     * @param {number} materialIndex
     * @return {Promise<THREE.Material>}
     */
    GLTFParser.prototype.loadMaterial = function (materialIndex) {

      var parser = this;
      var json = this.json;
      var extensions = this.extensions;
      var materialDef = json.materials[materialIndex];

      var materialType;
      var materialParams = {};
      var materialExtensions = materialDef.extensions || {};

      var pending = [];

      if (materialExtensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS]) {

        var sgExtension = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS];
        materialType = sgExtension.getMaterialType();
        pending.push(sgExtension.extendParams(materialParams, materialDef, parser));

      } else if (materialExtensions[EXTENSIONS.KHR_MATERIALS_UNLIT]) {

        var kmuExtension = extensions[EXTENSIONS.KHR_MATERIALS_UNLIT];
        materialType = kmuExtension.getMaterialType();
        pending.push(kmuExtension.extendParams(materialParams, materialDef, parser));

      } else {

        // Specification:
        // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

        materialType = THREE.MeshStandardMaterial;

        var metallicRoughness = materialDef.pbrMetallicRoughness || {};

        materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
        materialParams.opacity = 1.0;

        if (Array.isArray(metallicRoughness.baseColorFactor)) {

          var array = metallicRoughness.baseColorFactor;

          materialParams.color.fromArray(array);
          materialParams.opacity = array[3];

        }

        if (metallicRoughness.baseColorTexture !== undefined) {

          pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture));

        }

        materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
        materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;

        if (metallicRoughness.metallicRoughnessTexture !== undefined) {

          pending.push(parser.assignTexture(materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture));
          pending.push(parser.assignTexture(materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture));

        }

      }

      if (materialDef.doubleSided === true) {

        materialParams.side = THREE.DoubleSide;

      }

      var alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;

      if (alphaMode === ALPHA_MODES.BLEND) {

        materialParams.transparent = true;

      } else {

        materialParams.transparent = false;

        if (alphaMode === ALPHA_MODES.MASK) {

          materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;

        }

      }

      if (materialDef.normalTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

        pending.push(parser.assignTexture(materialParams, 'normalMap', materialDef.normalTexture));

        materialParams.normalScale = new THREE.Vector2(1, 1);

        if (materialDef.normalTexture.scale !== undefined) {

          materialParams.normalScale.set(materialDef.normalTexture.scale, materialDef.normalTexture.scale);

        }

      }

      if (materialDef.occlusionTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

        pending.push(parser.assignTexture(materialParams, 'aoMap', materialDef.occlusionTexture));

        if (materialDef.occlusionTexture.strength !== undefined) {

          materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;

        }

      }

      if (materialDef.emissiveFactor !== undefined && materialType !== THREE.MeshBasicMaterial) {

        materialParams.emissive = new THREE.Color().fromArray(materialDef.emissiveFactor);

      }

      if (materialDef.emissiveTexture !== undefined && materialType !== THREE.MeshBasicMaterial) {

        pending.push(parser.assignTexture(materialParams, 'emissiveMap', materialDef.emissiveTexture));

      }

      return Promise.all(pending).then(function () {

        var material;

        if (materialType === THREE.ShaderMaterial) {

          material = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].createMaterial(materialParams);

        } else {

          material = new materialType(materialParams);

        }

        if (materialDef.name !== undefined) material.name = materialDef.name;

        // baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
        if (material.map) material.map.encoding = THREE.sRGBEncoding;
        if (material.emissiveMap) material.emissiveMap.encoding = THREE.sRGBEncoding;
        if (material.specularMap) material.specularMap.encoding = THREE.sRGBEncoding;

        assignExtrasToUserData(material, materialDef);

        if (materialDef.extensions) addUnknownExtensionsToUserData(extensions, material, materialDef);

        return material;

      });

    };

    /**
     * @param {THREE.BufferGeometry} geometry
     * @param {GLTF.Primitive} primitiveDef
     * @param {GLTFParser} parser
     * @return {Promise<THREE.BufferGeometry>}
     */
    function addPrimitiveAttributes(geometry, primitiveDef, parser) {

      var attributes = primitiveDef.attributes;

      var pending = [];

      function assignAttributeAccessor(accessorIndex, attributeName) {

        return parser.getDependency('accessor', accessorIndex)
          .then(function (accessor) {

            geometry.addAttribute(attributeName, accessor);

          });

      }

      for (var gltfAttributeName in attributes) {

        var threeAttributeName = ATTRIBUTES[gltfAttributeName] || gltfAttributeName.toLowerCase();

        // Skip attributes already provided by e.g. Draco extension.
        if (threeAttributeName in geometry.attributes) continue;

        pending.push(assignAttributeAccessor(attributes[gltfAttributeName], threeAttributeName));

      }

      if (primitiveDef.indices !== undefined && !geometry.index) {

        var accessor = parser.getDependency('accessor', primitiveDef.indices).then(function (accessor) {

          geometry.setIndex(accessor);

        });

        pending.push(accessor);

      }

      assignExtrasToUserData(geometry, primitiveDef);

      return Promise.all(pending).then(function () {

        return primitiveDef.targets !== undefined
          ? addMorphTargets(geometry, primitiveDef.targets, parser)
          : geometry;

      });

    }

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
     *
     * Creates BufferGeometries from primitives.
     *
     * @param {Array<GLTF.Primitive>} primitives
     * @return {Promise<Array<THREE.BufferGeometry>>}
     */
    GLTFParser.prototype.loadGeometries = function (primitives) {

      var parser = this;
      var extensions = this.extensions;
      var cache = this.primitiveCache;

      function createDracoPrimitive(primitive) {

        return extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
          .decodePrimitive(primitive, parser)
          .then(function (geometry) {

            return addPrimitiveAttributes(geometry, primitive, parser);

          });

      }

      var pending = [];

      for (var i = 0, il = primitives.length; i < il; i++) {

        var primitive = primitives[i];
        var cacheKey = createPrimitiveKey(primitive);

        // See if we've already created this geometry
        var cached = cache[cacheKey];

        if (cached) {

          // Use the cached geometry if it exists
          pending.push(cached.promise);

        } else {

          var geometryPromise;

          if (primitive.extensions && primitive.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]) {

            // Use DRACO geometry if available
            geometryPromise = createDracoPrimitive(primitive);

          } else {

            // Otherwise create a new geometry
            geometryPromise = addPrimitiveAttributes(new THREE.BufferGeometry(), primitive, parser);

          }

          // Cache this geometry
          cache[cacheKey] = { primitive: primitive, promise: geometryPromise };

          pending.push(geometryPromise);

        }

      }

      return Promise.all(pending);

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
     * @param {number} meshIndex
     * @return {Promise<THREE.Group|THREE.Mesh|THREE.SkinnedMesh>}
     */
    GLTFParser.prototype.loadMesh = function (meshIndex) {

      var parser = this;
      var json = this.json;

      var meshDef = json.meshes[meshIndex];
      var primitives = meshDef.primitives;

      var pending = [];

      for (var i = 0, il = primitives.length; i < il; i++) {

        var material = primitives[i].material === undefined
          ? createDefaultMaterial()
          : this.getDependency('material', primitives[i].material);

        pending.push(material);

      }

      return Promise.all(pending).then(function (originalMaterials) {

        return parser.loadGeometries(primitives).then(function (geometries) {

          var meshes = [];

          for (var i = 0, il = geometries.length; i < il; i++) {

            var geometry = geometries[i];
            var primitive = primitives[i];

            // 1. create Mesh

            var mesh;

            var material = originalMaterials[i];

            if (primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
              primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
              primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
              primitive.mode === undefined) {

              // .isSkinnedMesh isn't in glTF spec. See .markDefs()
              mesh = meshDef.isSkinnedMesh === true
                ? new THREE.SkinnedMesh(geometry, material)
                : new THREE.Mesh(geometry, material);

              if (mesh.isSkinnedMesh === true && !mesh.geometry.attributes.skinWeight.normalized) {

                // we normalize floating point skin weight array to fix malformed assets (see #15319)
                // it's important to skip this for non-float32 data since normalizeSkinWeights assumes non-normalized inputs
                mesh.normalizeSkinWeights();

              }

              if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP) {

                mesh.drawMode = THREE.TriangleStripDrawMode;

              } else if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN) {

                mesh.drawMode = THREE.TriangleFanDrawMode;

              }

            } else if (primitive.mode === WEBGL_CONSTANTS.LINES) {

              mesh = new THREE.LineSegments(geometry, material);

            } else if (primitive.mode === WEBGL_CONSTANTS.LINE_STRIP) {

              mesh = new THREE.Line(geometry, material);

            } else if (primitive.mode === WEBGL_CONSTANTS.LINE_LOOP) {

              mesh = new THREE.LineLoop(geometry, material);

            } else if (primitive.mode === WEBGL_CONSTANTS.POINTS) {

              mesh = new THREE.Points(geometry, material);

            } else {

              throw new Error('THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode);

            }

            if (Object.keys(mesh.geometry.morphAttributes).length > 0) {

              updateMorphTargets(mesh, meshDef);

            }

            mesh.name = meshDef.name || ('mesh_' + meshIndex);

            if (geometries.length > 1) mesh.name += '_' + i;

            assignExtrasToUserData(mesh, meshDef);

            parser.assignFinalMaterial(mesh);

            meshes.push(mesh);

          }

          if (meshes.length === 1) {

            return meshes[0];

          }

          var group = new THREE.Group();

          for (var i = 0, il = meshes.length; i < il; i++) {

            group.add(meshes[i]);

          }

          return group;

        });

      });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
     * @param {number} cameraIndex
     * @return {Promise<THREE.Camera>}
     */
    GLTFParser.prototype.loadCamera = function (cameraIndex) {

      var camera;
      var cameraDef = this.json.cameras[cameraIndex];
      var params = cameraDef[cameraDef.type];

      if (!params) {

        console.warn('THREE.GLTFLoader: Missing camera parameters.');
        return;

      }

      if (cameraDef.type === 'perspective') {

        camera = new THREE.PerspectiveCamera(THREE.Math.radToDeg(params.yfov), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6);

      } else if (cameraDef.type === 'orthographic') {

        camera = new THREE.OrthographicCamera(params.xmag / - 2, params.xmag / 2, params.ymag / 2, params.ymag / - 2, params.znear, params.zfar);

      }

      if (cameraDef.name !== undefined) camera.name = cameraDef.name;

      assignExtrasToUserData(camera, cameraDef);

      return Promise.resolve(camera);

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
     * @param {number} skinIndex
     * @return {Promise<Object>}
     */
    GLTFParser.prototype.loadSkin = function (skinIndex) {

      var skinDef = this.json.skins[skinIndex];

      var skinEntry = { joints: skinDef.joints };

      if (skinDef.inverseBindMatrices === undefined) {

        return Promise.resolve(skinEntry);

      }

      return this.getDependency('accessor', skinDef.inverseBindMatrices).then(function (accessor) {

        skinEntry.inverseBindMatrices = accessor;

        return skinEntry;

      });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
     * @param {number} animationIndex
     * @return {Promise<THREE.AnimationClip>}
     */
    GLTFParser.prototype.loadAnimation = function (animationIndex) {

      var json = this.json;

      var animationDef = json.animations[animationIndex];

      var pendingNodes = [];
      var pendingInputAccessors = [];
      var pendingOutputAccessors = [];
      var pendingSamplers = [];
      var pendingTargets = [];

      for (var i = 0, il = animationDef.channels.length; i < il; i++) {

        var channel = animationDef.channels[i];
        var sampler = animationDef.samplers[channel.sampler];
        var target = channel.target;
        var name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
        var input = animationDef.parameters !== undefined ? animationDef.parameters[sampler.input] : sampler.input;
        var output = animationDef.parameters !== undefined ? animationDef.parameters[sampler.output] : sampler.output;

        pendingNodes.push(this.getDependency('node', name));
        pendingInputAccessors.push(this.getDependency('accessor', input));
        pendingOutputAccessors.push(this.getDependency('accessor', output));
        pendingSamplers.push(sampler);
        pendingTargets.push(target);

      }

      return Promise.all([

        Promise.all(pendingNodes),
        Promise.all(pendingInputAccessors),
        Promise.all(pendingOutputAccessors),
        Promise.all(pendingSamplers),
        Promise.all(pendingTargets)

      ]).then(function (dependencies) {

        var nodes = dependencies[0];
        var inputAccessors = dependencies[1];
        var outputAccessors = dependencies[2];
        var samplers = dependencies[3];
        var targets = dependencies[4];

        var tracks = [];

        for (var i = 0, il = nodes.length; i < il; i++) {

          var node = nodes[i];
          var inputAccessor = inputAccessors[i];
          var outputAccessor = outputAccessors[i];
          var sampler = samplers[i];
          var target = targets[i];

          if (node === undefined) continue;

          node.updateMatrix();
          node.matrixAutoUpdate = true;

          var TypedKeyframeTrack;

          switch (PATH_PROPERTIES[target.path]) {

            case PATH_PROPERTIES.weights:

              TypedKeyframeTrack = THREE.NumberKeyframeTrack;
              break;

            case PATH_PROPERTIES.rotation:

              TypedKeyframeTrack = THREE.QuaternionKeyframeTrack;
              break;

            case PATH_PROPERTIES.position:
            case PATH_PROPERTIES.scale:
            default:

              TypedKeyframeTrack = THREE.VectorKeyframeTrack;
              break;

          }

          var targetName = node.name ? node.name : node.uuid;

          var interpolation = sampler.interpolation !== undefined ? INTERPOLATION[sampler.interpolation] : THREE.InterpolateLinear;

          var targetNames = [];

          if (PATH_PROPERTIES[target.path] === PATH_PROPERTIES.weights) {

            // Node may be a THREE.Group (glTF mesh with several primitives) or a THREE.Mesh.
            node.traverse(function (object) {

              if (object.isMesh === true && object.morphTargetInfluences) {

                targetNames.push(object.name ? object.name : object.uuid);

              }

            });

          } else {

            targetNames.push(targetName);

          }

          var outputArray = outputAccessor.array;

          if (outputAccessor.normalized) {

            var scale;

            if (outputArray.constructor === Int8Array) {

              scale = 1 / 127;

            } else if (outputArray.constructor === Uint8Array) {

              scale = 1 / 255;

            } else if (outputArray.constructor == Int16Array) {

              scale = 1 / 32767;

            } else if (outputArray.constructor === Uint16Array) {

              scale = 1 / 65535;

            } else {

              throw new Error('THREE.GLTFLoader: Unsupported output accessor component type.');

            }

            var scaled = new Float32Array(outputArray.length);

            for (var j = 0, jl = outputArray.length; j < jl; j++) {

              scaled[j] = outputArray[j] * scale;

            }

            outputArray = scaled;

          }

          for (var j = 0, jl = targetNames.length; j < jl; j++) {

            var track = new TypedKeyframeTrack(
              targetNames[j] + '.' + PATH_PROPERTIES[target.path],
              inputAccessor.array,
              outputArray,
              interpolation
            );

            // Override interpolation with custom factory method.
            if (sampler.interpolation === 'CUBICSPLINE') {

              track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline(result) {

                // A CUBICSPLINE keyframe in glTF has three output values for each input value,
                // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
                // must be divided by three to get the interpolant's sampleSize argument.

                return new GLTFCubicSplineInterpolant(this.times, this.values, this.getValueSize() / 3, result);

              };

              // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
              track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;

            }

            tracks.push(track);

          }

        }

        var name = animationDef.name !== undefined ? animationDef.name : 'animation_' + animationIndex;

        return new THREE.AnimationClip(name, undefined, tracks);

      });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
     * @param {number} nodeIndex
     * @return {Promise<THREE.Object3D>}
     */
    GLTFParser.prototype.loadNode = function (nodeIndex) {

      var json = this.json;
      var extensions = this.extensions;
      var parser = this;

      var meshReferences = json.meshReferences;
      var meshUses = json.meshUses;

      var nodeDef = json.nodes[nodeIndex];

      return (function () {

        var pending = [];

        if (nodeDef.mesh !== undefined) {

          pending.push(parser.getDependency('mesh', nodeDef.mesh).then(function (mesh) {

            var node;

            if (meshReferences[nodeDef.mesh] > 1) {

              var instanceNum = meshUses[nodeDef.mesh]++;

              node = mesh.clone();
              node.name += '_instance_' + instanceNum;

              // onBeforeRender copy for Specular-Glossiness
              node.onBeforeRender = mesh.onBeforeRender;

              for (var i = 0, il = node.children.length; i < il; i++) {

                node.children[i].name += '_instance_' + instanceNum;
                node.children[i].onBeforeRender = mesh.children[i].onBeforeRender;

              }

            } else {

              node = mesh;

            }

            // if weights are provided on the node, override weights on the mesh.
            if (nodeDef.weights !== undefined) {

              node.traverse(function (o) {

                if (!o.isMesh) return;

                for (var i = 0, il = nodeDef.weights.length; i < il; i++) {

                  o.morphTargetInfluences[i] = nodeDef.weights[i];

                }

              });

            }

            return node;

          }));

        }

        if (nodeDef.camera !== undefined) {

          pending.push(parser.getDependency('camera', nodeDef.camera));

        }

        if (nodeDef.extensions
          && nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL]
          && nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light !== undefined) {

          pending.push(parser.getDependency('light', nodeDef.extensions[EXTENSIONS.KHR_LIGHTS_PUNCTUAL].light));

        }

        return Promise.all(pending);

      }()).then(function (objects) {

        var node;

        // .isBone isn't in glTF spec. See .markDefs
        if (nodeDef.isBone === true) {

          node = new THREE.Bone();

        } else if (objects.length > 1) {

          node = new THREE.Group();

        } else if (objects.length === 1) {

          node = objects[0];

        } else {

          node = new THREE.Object3D();

        }

        if (node !== objects[0]) {

          for (var i = 0, il = objects.length; i < il; i++) {

            node.add(objects[i]);

          }

        }

        if (nodeDef.name !== undefined) {

          node.userData.name = nodeDef.name;
          node.name = THREE.PropertyBinding.sanitizeNodeName(nodeDef.name);

        }

        assignExtrasToUserData(node, nodeDef);

        if (nodeDef.extensions) addUnknownExtensionsToUserData(extensions, node, nodeDef);

        if (nodeDef.matrix !== undefined) {

          var matrix = new THREE.Matrix4();
          matrix.fromArray(nodeDef.matrix);
          node.applyMatrix(matrix);

        } else {

          if (nodeDef.translation !== undefined) {

            node.position.fromArray(nodeDef.translation);

          }

          if (nodeDef.rotation !== undefined) {

            node.quaternion.fromArray(nodeDef.rotation);

          }

          if (nodeDef.scale !== undefined) {

            node.scale.fromArray(nodeDef.scale);

          }

        }

        return node;

      });

    };

    /**
     * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
     * @param {number} sceneIndex
     * @return {Promise<THREE.Scene>}
     */
    GLTFParser.prototype.loadScene = function () {

      // scene node hierachy builder

      function buildNodeHierachy(nodeId, parentObject, json, parser) {

        var nodeDef = json.nodes[nodeId];

        return parser.getDependency('node', nodeId).then(function (node) {

          if (nodeDef.skin === undefined) return node;

          // build skeleton here as well

          var skinEntry;

          return parser.getDependency('skin', nodeDef.skin).then(function (skin) {

            skinEntry = skin;

            var pendingJoints = [];

            for (var i = 0, il = skinEntry.joints.length; i < il; i++) {

              pendingJoints.push(parser.getDependency('node', skinEntry.joints[i]));

            }

            return Promise.all(pendingJoints);

          }).then(function (jointNodes) {

            node.traverse(function (mesh) {

              if (!mesh.isMesh) return;

              var bones = [];
              var boneInverses = [];

              for (var j = 0, jl = jointNodes.length; j < jl; j++) {

                var jointNode = jointNodes[j];

                if (jointNode) {

                  bones.push(jointNode);

                  var mat = new THREE.Matrix4();

                  if (skinEntry.inverseBindMatrices !== undefined) {

                    mat.fromArray(skinEntry.inverseBindMatrices.array, j * 16);

                  }

                  boneInverses.push(mat);

                } else {

                  console.warn('THREE.GLTFLoader: Joint "%s" could not be found.', skinEntry.joints[j]);

                }

              }

              mesh.bind(new THREE.Skeleton(bones, boneInverses), mesh.matrixWorld);

            });

            return node;

          });

        }).then(function (node) {

          // build node hierachy

          parentObject.add(node);

          var pending = [];

          if (nodeDef.children) {

            var children = nodeDef.children;

            for (var i = 0, il = children.length; i < il; i++) {

              var child = children[i];
              pending.push(buildNodeHierachy(child, node, json, parser));

            }

          }

          return Promise.all(pending);

        });

      }

      return function loadScene(sceneIndex) {

        var json = this.json;
        var extensions = this.extensions;
        var sceneDef = this.json.scenes[sceneIndex];
        var parser = this;

        var scene = new THREE.Scene();
        if (sceneDef.name !== undefined) scene.name = sceneDef.name;

        assignExtrasToUserData(scene, sceneDef);

        if (sceneDef.extensions) addUnknownExtensionsToUserData(extensions, scene, sceneDef);

        var nodeIds = sceneDef.nodes || [];

        var pending = [];

        for (var i = 0, il = nodeIds.length; i < il; i++) {

          pending.push(buildNodeHierachy(nodeIds[i], scene, json, parser));

        }

        return Promise.all(pending).then(function () {

          return scene;

        });

      };

    }();

    return GLTFLoader;

  })();
}